They said the air strike hit Daglun, a village near Nigeria's border with Cameroon. Islamic extremists killed nearly 100 people in that area this week.

Military spokesman Captain Jafaru Nuru said he was unaware that any bombs killed civilians.

An elderly resident of Daglun said he was sitting under a tree when he saw bombs dropping from a military aircraft. A nurse at the local hospital said it received many dead and wounded, and a community leader said 20 people died.

Jets have been bombing the area for weeks as part of a nine-month effort to suppress an Islamic insurgency in Africa's biggest oil producer.